1. Field of the Invention
This invention relates to a semiconductor memory device and a method of controlling the semiconductor memory device, and more particularly to a semiconductor memory with memory cell including a charge storage layer and a control gate.
2. Description of the Related Art
An electrically erasable and programmable ROM (EEPROM) has been known as a nonvolatile semiconductor memory capable of rewriting data electrically. Some EEPROMs have an automatic operating function and a synchronous reading function capable of being executed simultaneously with the automatic operating function. Such an EEPROM has been disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 2003-196987.
The automatic operating function is the function of writing and erasing data automatically by externally inputting a command. The synchronous reading function is the function of reading data in synchronization with a clock by externally inputting a command.
In an EEPROM having the automatic operating function and synchronous reading function, the memory cell array is divided into banks. When a bank in an automatic operation is accessed for synchronous reading, a sequence flag is externally output in place of read data. From the sequence flag, it is recognized that the bank is in an automatic operation and therefore is inhibited from being accessed.
However, with a conventional EEPROM, if the automatic operation ends immediately after a synchronous read operation has started, the sequence flag might not be output properly, resulting in a malfunction.